Sift together flour, baking powder and salt in medium bowl. In large bowl cream butter. Gradually add sugar; beat until fluffy. Add eggs one at a time, beating well after each addition. Mix in lemon zest, juice and thyme. Alternately add dry ingredients and half-and-half to butter mixture, mixing just until batter is blended. Pour batter into 8-inch loaf pan and bake for 55-60 minutes in preheated 350° oven, until pick inserted into center comes out clean. Let stand in pan for five minutes, then turn out onto wire rack. A glaze of two tablespoons fresh lemon juice and 1/2 cup powdered sugar may be poured slowly over warm loaf. Let cool completely.